#define A 2
#define B 3
#define C 4
#define D 5
#define E 6
#define F 7
#define G 8
#define DP 9 
#define CA1 0
#define CA2 1
#define dly 500

const char segs[8] = {A,B,C,D,E,F,G,DP};
const byte numbers[10] = { 
  0b1000000, 
  0b1111001,
  0b0100100,
  0b0110000, 
  0b0011001, 
  0b0010010,
  0b0000010, 
  0b1111000, 
  0b0000000, 
  0b0010000
};

void setup() {
  pinMode(A, OUTPUT);
  pinMode(B, OUTPUT);
  pinMode(C, OUTPUT);
  pinMode(D, OUTPUT);
  pinMode(E, OUTPUT);
  pinMode(F, OUTPUT);
  pinMode(G, OUTPUT);
  pinMode(DP, OUTPUT);
  pinMode(CA1, OUTPUT);
  pinMode(CA2, OUTPUT);
}

void loop() {
  for (int digit1 = 0; digit1 < 10; digit1++) {
    for (int digit2 = 0; digit2 < 10; digit2++) {
      unsigned long startTime = millis();
      for (unsigned long elapsed = 0; elapsed < 600; elapsed = millis() - startTime) {
        lightDigit1(numbers[digit1]);
        delay(dly);
        lightDigit2(numbers[digit2]);
        delay(dly);
      }
    }
  }
}

void lightDigit1(byte number) {
  digitalWrite(CA1, HIGH);
  digitalWrite(CA2, LOW);
  lightSegments(number);
}
void lightDigit2(byte number) {
  digitalWrite(CA1, LOW);
  digitalWrite(CA2, HIGH);
  lightSegments(number);
}

void lightSegments(byte number) {
  for (int i = 0; i < 8; i++) {
    int bit = bitRead(number, i);
    digitalWrite(segs[i], bit);
  }
}